1. Field of the Invention
The present invention relates to a wire harness including an electric cable and a double-layered corrugated tube.
2. Description of the Related Art
Wire harnesses are laid in a vehicle such as a motor vehicle for effecting electrical connections. Wire harnesses are widely known in which thin electric wires are bound together. In addition, in recent years, wire harnesses are also known which include thick high voltage cables for electric vehicles or hybrid vehicles. There are also known wire harnesses which include an electric wire or cable protection corrugated tube in addition to those conventional constituent members. Patent Document 1 below discloses a wire harness which employs a technique in which a bundle of electric wires is protected by a corrugated tube and thereafter, a predetermined portion of the corrugated tube is protected further by another corrugated tube. Namely, the wire harness is disclosed therein which employs the technique in which the double-layered corrugated tube construction is partially adopted.
A slit is formed in the corrugated tube of Patent Document 1 below for allowing the insertion of the bundle of electric wires into the corrugated tube. Because of this, in the event that there is provided only one corrugated tube, there exists a possibility that an external interference material enters an interior of the corrugated tube. Should the external interference material enter the interior of the corrugated tube, the electric wires are damaged by the external interference material. The wire harness disclosed in Patent Document 1 below is intended not only to prevent the entrance of the external interference material but also to prevent the damage of the electric wires and proposes the double-layered construction in which the slit in the corrugated tube is covered to be concealed by the additional corrugated tube.
The additional corrugated tube, that is, the outer corrugated tube is disposed so that its own slit is not registered with the slit position of the inner corrugated tube. The outer corrugated tube is fixed with a tape which is wound therearound.
Patent Document 1: JP-A-2000-197237
In the related art described above, the bundle of electric wires is inserted into the inner corrugated tube through the slit formed therein, and thereafter, the outer corrugated tube is assembled on to the predetermined portion of the inner corrugated tube. Specifically, at first, the slit in the outer corrugated tube is opened, and then, the inner corrugated tube is inserted into the outer corrugated tube through the slit so opened. Finally, the tape is wound round the outer corrugated tube so as to fix it in place.
As is seen from the description of the work involved, in the related art wire harness, the work becomes complex, resulting in a problem that the workability is not good. In addition, in the related art wire harness, both the outer corrugated tube and the inner corrugated tube have the slits, resulting in a problem that water or foreign matters tend to easily enter interiors thereof. When water or foreign matters tend to easily enter the interiors of those corrugated tubes, it is difficult to lay the tubes on the outer side of a vehicle, for example.
Incidentally, corrugated tubes for protecting electric wires have the following problem. Namely, when a wire harness is laid in a position on a vehicle where vibrations are easily transmitted thereto from the vehicle, there is caused a problem that depending on conditions under which electric wires are accommodated in a corrugated tube, the wear of the corrugated tube is induced. Hereinafter, this wearing problem will be described specifically by reference to FIG. 6.
In FIG. 6, a corrugated tube 1 has ridge portions 2 and groove portions 3 which continue alternately. The corrugated tube 1 is formed so that an interior space thereof becomes an accommodation space of an electric wire 5. An inside diameter of the corrugated tube 1 is determined by the groove portions 3. An outside diameter of the electric wire 5 is smaller than the inside diameter of the corrugated tube 1. When a space between the groove portions 3 and the electric wire 5 becomes large, the electric wire 5 is struck against the groove portions 3 largely and repeatedly by vibrations transmitted to the corrugated tube 1 from the vehicle. Namely, there are caused strong or violent contacts (refer to imaginary lines in the figure), and it is confirmed from experiments that wear 6 is caused on the groove portions 3. In addition, it is also confirmed that the covering of the electric wire 5 is slightly worn out.
Depending on the extent of the wear 6, there is cased a problem that water or foreign matters enter an interior of the corrugated tube 1 from an exterior portion in case the wear 6 is so serious as to open a hole in the corrugated tube 1. In case it is concerned that the corrugated tube 1 has a defect of entrance of water or foreign matters, this will lead to a problem that the protection of the electric wire 5 is insufficient.